Are they adult discus? If so, I wouldn't worry much about it at all.
If they're juvies, you gotta take people's advice with a grain of salt. Hardcore discus folk will mostly tell you how to care for your fish at OPTIMAL conditions so that your fish will grow 8+ inches, mate with an equally beautiful partner, and win you awards in international competitions. OK, maybe a little sarcasm, but you get the point.
Personally, I don't think gradual ph swings like that will hurt, especially with non-wilds. Will you grow out 8" discus? Probably not, but they're still awesome fish even if they only reach 5".
65g planted tank - 200W heat - PC 192W/6700K - Eheim 2217 - Pressurized CO2 - EI Dosing